Stent cell configurations including spirals

ABSTRACT

The invention is directed to an expandable stent which is longitudinally flexible in both the unexpanded and expanded conditions. The stent includes spiral structures which at least partially unwind upon expansion of the stent to limit stent recoil. Regions of low strain in the stent during expansion are provided by the spiral structures.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of application Ser. No. 09/389,832filed Sep. 3, 1999, issued as U.S. Pat. No. 6,334,870 Jan. 1, 2002,which is a continuation of PCT/US98/08275 filed Apr. 24, 1998 which is aContinuation of application Ser. No. 08/846,164 filed Apr. 25, 1997,issued as U.S. Pat. No. 6,033,433 Mar. 7, 2000, the disclosures of whichare hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to stents of improved configuration whichincorporate spiral articulations which unwind to form bracing structuresor scaffolding upon expansion.

2. Brief Description of the Prior Art

Stents are radially expandable endoprosthesis which are typicallyintravascular implants capable of being implanted transluminally andenlarged radially after being introduced percutaneously. They have alsobeen implanted in urinary tracts and bile ducts. They are used toreinforce body vessels and to prevent restenosis following angioplastyin the vascular system. They may be self-expanding or expanded by aninternal radial force, such as when mounted on a balloon.

In the past, stents have assumed many configurations and been made ofmany materials, including metals and plastic. Ordinary metals such asstainless steel have been used as have shape memory metals such asnitinol and the like. Stents have also been made of biodegradableplastic materials. They have been formed from wire, tube stock, etc.

SUMMARY OF THE INVENTION

This invention provides a new configuration for stents which may beadapted by all of the various types of prior art stents referred tohereinabove. There are numerous advantages to the new configuration. Itlimits recoil and adds resistance to compression for the expanded stent,among other things. It is longitudinally flexible in both the unexpandedand expanded conditions. It has several embodiments.

An important part of the new configuration includes a spiral orspiral-like structure comprised of joined elements which are coiled orbent and which unwind, uncoil or unbend to a more or less straightenedcondition on expansion of the stent. Such structures are hereinafterreferred to collectively as spirals, spirals or spiral-like structures.These structures provide regions of low strain in the stent duringexpansion. These elements may be joined to each other or to any radiallyexpansive members of any kind, annular serpentine members beingpreferred.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a flat view of one pattern embodiment of a stent configurationof the invention (unexpanded);

FIG. 2 is a detail of a portion of FIG. 1;

FIG. 3 is an end view of a stent of the FIG. 1 pattern according to theinvention showing it in tubular configuration;

FIG. 4 is a showing of a stent in the embodiment of the precedingFigures in perspective and in an unexpanded configuration;

FIG. 5 is a showing of the stent of FIG. 4 fully expanded with detailsof the front and rear of the stent;

FIGS. 6, 7 and 8 are showings of the stent of FIG. 4 in various stagesof expansion with only details of the front of the stent shown forsimplicity;

FIG. 9 is a plan view showing another embodiment of the invention;

FIG. 10 is a showing of a modified embodiment;

FIG. 11 is a showing of another embodiment;

FIG. 12 is a detail of a portion of FIG. 11;

FIG. 13 is a showing of the stent of FIGS. 11 and 12 in an expandedconfiguration;

FIG. 14 is a showing of another embodiment;

FIG. 15 is a showing of still another embodiment;

FIG. 16 is a showing of yet another embodiment;

FIG. 17 is a showing of still another embodiment;

FIGS. 18-28 show various spiral-like arrangements of the invention;

FIG. 29 shows another embodiment of the invention;

FIG. 30 shows yet another embodiment; and

FIG. 31 shows still another embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

One preferred embodiment of the invention is illustrated in FIGS. 1-8.It comprises a metal tube-like structure 10 as best shown in FIGS. 3 and4, such as nitinol or stainless steel, which has been etched or lasercut to the configuration shown in the plan view of FIGS. 1 and 2 and ina short version as shown in FIG. 4. The configuration is made up of aseries of serpentine annular expandable elements or segments 12 whichform loops 14 to allow for radial annular expansion. Segments 12 may beother configurations but serpentine is preferred. Elements 12 areinterconnected by pairs of elongated members 13 a and 13 b which areattached at one end to successive loops 14 of a segment 12 and which arejoined at their other ends to adjacent pairs of elongated members 13 aand 13 b, as best seen in detail in FIG. 2. Members 13 a and 13 b arepreferably of narrower gauge than members 12 and are joined together ina coiled or spiral arrangement as shown generally at 16. Spiral 16 formsa structure about which members 13 may uncoil or unwind in acounterclockwise direction or clockwise direction to a substantiallystraight condition, depending on the spiral winding direction, uponradial expansion of members 12. In this embodiment spirals 16 are formedin alternate wound structures so that some unwind in one direction andsome in the other direction. Of course, in any embodiment the spiralscan be formed so that they all unwind in one direction, either clockwiseor counterclockwise and they may have more or fewer members 13. Also,more or less spirals may be included between the segments. The unwindingis accompanied by a straightening action with respect to members 13 asis described in more detail in connection with FIGS. 4-8. It can be seenfrom FIGS. 4 through 8 that the resultant configuration in an expandedstent of this configuration is comprised of a plurality of cells, theperimeter of each of which is defined by a pair of members or strutsdefined by the loop portion 14 of segment 12 and a pair of members orstruts 13. The cells are joined at 16 as best seen in FIG. 8. Morespecifically the cells are of two kinds as shown in FIG. 8. A first pairof cells are A and B made up of a segment 12 and two struts 13 a forcell A or 13 b for cell B. A second pair of cells are C and D made up ofan inward loop portion 14 of segment 12 and a strut 13 a and a strut 13b for cells C and D.

When a stent of the invention, such as that shown in FIGS. 1-4 undergoesexpansion, such as from the embodiment of FIG. 4, it will appear asshown in FIG. 5 in the fully expanded condition. FIG. 5 shows the stentin perspective.

The unwinding action which the coil elements 16 undergo upon stentexpansion is best seen in FIGS. 6-8 which show only the front sidesurface of the stent for simplicity and clarity.

As radial expansion begins (seen in FIG. 6) it can be appreciated thatthe spiral elements 16 undergo an unwinding or straightening action by apulling force on all of the members 13. Specifically, as expansionoccurs, elements 13 undergo a straightening action as can be seen in theearly stages of expansion in FIG. 6.

Upon further expansion (seen in FIG. 7), spirals 16 undergo furtherunwinding, i.e., elements 13 undergo further straightening.

Finally in FIG. 8, substantial full expansion provides substantiallystraightened elements 13 which in that condition limit stent recoil andincrease the resistance to compression of the stent.

FIG. 9 shows a modified embodiment in which elements 13 a and 13 bcontact segment 12 at the end of its loops 14. Also note in thisembodiment that the spirals 16 are all wound in the same direction.

FIG. 10 shows an embodiment of the invention in which the spiral members13 are more bent and less curvilinear but still form a spiral-likeconfiguration 16. The remainder of the configuration is similar to thatof FIG. 9. In FIG. 10, elongate members 13 are shown prior to expansionof the stent. When the stent is expanded, members 13 unwindcounter-clockwise and straighten somewhat. At full expansion members 13straighten still further and straighten substantially so as to provideresistance to compression of the stent and low recoil. The expandedconfiguration displays a cell configuration similar to that seen in FIG.8.

Other embodiments are shown in subsequent Figures with different spiralarrangements. For example, the embodiment of FIGS. 11-13 shows coiledarrangements 16 which are wound in the same direction and elements 13attached at the end of loops 14 while some adjacent spirals betweensegments are interconnected by members 15.

FIG. 14 shows some elements 13 in a spiral 16 contacting the end ofloops 14 and some contacting segment 12 proper. Also, some adjacentspirals are interconnected by members 17.

FIG. 15 shows a flattened or elongated spiral arrangement 16 andelements 12 are angled with respect to the longitudinal axis of thestent. In previous embodiments, these elements or segments have beenarranged parallel to the axis or horizontal. Elongated spirals as inFIG. 13 and spirals of previous Figures may be mixed together. (Notshown).

In the embodiments already discussed, annular expandable segments suchas segments 12 are interspersed with spiral arrangements 16. However, ascan be seen in FIG. 16, at least a substantial portion or all of thestent body can be merely comprised of spiral arrangements 16 connectedto each other. Actually, all of the body may consist of spirals. In thisembodiment, the elements 13 interconnect between spirals oversubstantially the entire body of the stent. Optionally, the ends mayinclude segments 12 as shown.

The embodiment shown in FIG. 17 shows segments 12 alternately angled inopposite directions and with legs thereof of different length andelements 13 contacting the segments at different locations, i.e., as atthe loop portion 14 and at the segment portion proper.

FIGS. 18-28 demonstrate examples of what is meant by the terms spiraland spiral-like herein. Of course, additional members may be included inthe spirals.

FIG. 29 shows segments 12 in a configuration other than the annularserpentine configuration of previous Figures.

FIG. 30 shows alternate segments 12 in serpentine annular configurationinterconnected by double rows of interconnected coil configurations 16.

FIG. 31 is included to demonstrate that spirals 16 may be included onthe ends of a stent 10.

While this invention may be embodied in many different forms, there aredescribed in detail herein specific preferred embodiments of theinvention. This description is an exemplification of the principles ofthe invention and is not intended to limit the invention to theparticular embodiments illustrated.

The above Examples and disclosure are intended to be illustrative andnot exhaustive. These examples and description will suggest manyvariations and alternatives to one of ordinary skill in this art. Allthese alternatives and variations are intended to be included within thescope of the attached claims. Those familiar with the art may recognizeother equivalents to the specific embodiments described herein whichequivalents are also intended to be encompassed by the claims attachedhereto.

What is claimed is as follows:
 1. A stent having a longitudinal axis,the stent comprising a plurality of undulating bands disposed about thelongitudinal axis, each undulating baud having alternating peaks andtoughs with struts extending therebetween, the struts and troughsforming loops with an oblique angle therebetween the struts, linesbisecting the angle of the loops in the undulating band beingsubstantially parallel to one another, the struts non-parallel to thelongitudinal axis of the stern, the undulating bands which are adjacentone another being connected via a plurality of connectors, theconnectors arranged to form spiral configurations.
 2. The stent of claim1, wherein some of the struts have two connectors extending therefrom.3. The stern of claim wherein a plurality of struts are sloped relativeto the longitudinal axis of the stent.
 4. The stent of claim 3, whereinthe struts of adjacent bands are sloped in opposing directions.
 5. Thestem of claim 1, wherein adjacent struts of each undulating band arenon-parallel to one another.
 6. The stent of claim 1, wherein a portionof the connectors are attached to a peak of an undulating band and astrut of an undulating band.
 7. A stent having a longitudinal axis, thestent comprising a plurality of undulating bands disposed about thelongitudinal axis, each undulating band having alternating peaks andtroughs with corresponding stints extending there between, adjacentstruts defining openings which are aligned to the longitudinal axis ofthe stent, adjacent undulating bands being connected to one another viaa plurality of connectors, the connectors having elongate membersarranged to form a spiral and which upon expansion become straighter. 8.The stent of claim 7, wherein at least one undulating band has elongatemembers attached at locations longitudinally offset from one another. 9.The stent of claim 7, wherein two elongate members extend from eachpeak.
 10. The stent of claim 7, wherein the number of spiralsconfigurations between adjacent bands is equal to the number of peaks.11. The stent of claim 7, wherein one elongate member extends from eachpeak.
 12. The stent of claim 7, wherein the number of peaks in anundulating band is twice the number of spiral configurations in anadjacent connecting band.
 13. The stent of claim 7, wherein two elongatemembers extend from each of half of the peaks in an undulating band. 14.The stent of claim 7, wherein some of the peaks do not have any elongatemembers extending therefrom.
 15. The stent of claim 14, wherein thenumber of peaks in an undulating band are equal to the number of spiralconfigurations in an adjacent connecting band.
 16. The stent of claim 7,wherein a portion of the spiral configurations are directly attached toanother spiral configuration.
 17. The stent of claim 16, wherein atleast one elongate member is attached to a strut of an undulating bandand at least one elongate member is attached to a peak of an undulatingband.
 18. A stent having a longitudinal axis, the stent comprisingundulating bands disposed about the longitudinal axis, each undulatingband having alternating peaks and troughs with struts extendingtherebetween, the undulating bands which are adjacent one another beingconnected via connectors, the connectors arranged to form spiralconfigurations which unwind upon expansion of the stent.
 19. The stoatof claim 18, wherein the struts are non-parallel to the longitudinalaxis of the stent.
 20. A stent having a longitudinal axis, the stentcomprising undulating bands disposed about the longitudinal axis, eachundulating band having alternating peaks and troughs with strutsextending therebetween, undulating bands which are adjacent one anotherbeing connected via connectors, the connectors each having a firstsegment extending from one undulating band and a second segmentextending from an adjacent undulating band, the segments windinglyconverging at a center region of the connector, the connectors unwindingupon expansion of the stent.
 21. The stent of claim 20, wherein eachsegment extends beyond the center region of the connector and curvesback forward to the center region where the first and second segmentsjoin one another.